For example, Japanese Unexamined Patent Application Publication No. 4-137507 or Japanese Unexamined Patent Application Publication No. 2004-6696 discloses a wire wound-type inductor including a winding core part having a substantially taper-shaped portion, which is interesting for the present disclosure.
The wire wound-type inductor as disclosed in Japanese Unexamined Patent Application Publication No. 4-137507 includes a substantially circular cone-shaped main shaft made of a dielectric material and a winding wire one end of which is fixed to the top of the substantially circular cone-shaped main shaft and which is wound around the circumference of the main shaft in an adjacent manner such that the diameter thereof is gradually decreased.
The wire wound-type inductor as disclosed in Japanese Unexamined Patent Application Publication No. 2004-6696 includes a core formed by flange portions having substantially rectangular parallelepiped shapes at both end portions of a substantially taper-shaped cylindrical winding wire part, a winding wire wound around the outer circumferential surface of the winding wire part of the core, and an outer body having a substantially rectangular parallelepiped shape, which covers the core and the winding wire. Two outer electrode terminals are formed at lower positions on both side surfaces of the outer body in an adhesion manner and these outer electrode terminals and terminal portions formed on both end portions of the winding wire are connected to each other, respectively.
These wire wound-type inductors including the winding core part having the substantially taper-shaped portion can be used in a wide frequency range. As a reason for this, for example, Japanese Unexamined Patent Application Publication No. 4-137507 discloses that these inductors can reduce resonance points.